Smith has a rather tragic past, his biological father, a prominent medical researcher, thought he had discovered a way to cure previously incurable diseases. Instead, it turned out that Microbe had unknowingly used his mutant power and "talked" the diseases into acting out the results his father wanted. Disgraced, his father disowned Microbe, leaving the teen heartbroken and alone. Out of compassion Night Thrasher adopted him and began training him to be a superhero, making him a member of the New Warriors

While tracking some escaped supervillains with the New Warriors, Microbe, alongside his foster father Night Thrasher, are killed in Stamford, Connecticut as part of the New Warriors reality show. This event sparks the need for the Superhuman Registration Act and the ensuing Civil War, as well as making the surviving and former New Warriors members the most hated people in America